Method and apparatus for making sheet material



April 18, 1944. E M KRATZ 2,346,764

METHOD AND APPARATUS FOR MAKING SHEET MATERIAL Filed Sept. 12, 193B 9Sheets-Sheet 1 April 1s, 1944. E M KRATZ 2,346,764

METHOD AND APPARATUS FOR MAKING SHEET MATERIAL Filed Sept. 12, 1938 9Sheets-Sheet 2 HHHHII :QQ

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METHOD AND APPARATUS FOR MAKING SHEET MATERIAL Filed Sept. 12, 1958 9Sheets-Sheet 4 E. M KRA-rz Apri 1s, 1944.,

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E. M. RRA-rz l METHOD AND APPARATUS FOR MAKING ySHEET MATERIAL FlledSept 12, 1958 E. M. KRA-rz -pril 18, 1944.

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KQN MVN Patented Apr. 18, 1944 -METHOD AND APPARATUS FOR MAKING SHEETMATERIAL Edouard M. Kratz, Gary, Ind.,

assignor, by mesne assignments, to Carbide and Carbon ChemicalsCorporation, New York, N. Y.,

of New York a corporation Application September 12, 1938, Serial No.229,509

3 Claims.

This invention relates to an improved method and apparatus for makingwebs or sheets from lm forming materials such as casein or syntheticresin solutions, for example.

The main objects of the invention are to provide a method and apparatusby which high speed production of sheeting or webbing of the characterindicated may be carried on; to provide a method and apparatus for thepurpose indicated whereby a sheet or web of very thin but uniformthickness may be produced; to provide a method and means whereby a softand pliable sheet may be formed; and in general, it is the object ofthis invention to provide an improved method and apparatus for thepurpose indicated.

Other objects and advantages of the invention will be understood byreference to the following specification land accompanying drawings (9sheets) wherein there is illustrated the improved apparatus for makingsheet material by the improved method.

In the drawings:

. Figure 1 is a more or less diagrammaticrepresentation of the improvedapparatus.

Figures 2, 3 and 4 are longitudinal sections respectively, Figures 2 and4 illustrating the opposite end portions and Figure 3 illustrating theportions of the apparatus intermediate the opposite -end portions.

Figure 5 is a perspective illustrating the portions of the apparatuswhere the liquid material is delivered to it for formation into a sheet.

Figure 6 is a side elevation of the mechanism shown in Figure 5 togetherwith certain other mechanism at the receiving end of the apparatus.

Figure 'I is an elevation of an end portion of the apparatus asindicated by the line 'lof Figure 6.

Figure 8 is a sectional illustration showing in detail the arrangementfor delivering the liquid material to the apparatus and for forming thesheet from such liquid material.

Figure 9 is a perspective illustrating an arrangement for controllingsidewise shifting of a belt or band on which the sheet material is car-`ried for drying purposes.`

Figure 10 is a section on the line lll-I0 of Figure 3.

Figures l1 and 12 are sections respectively on thelines Il-H and I2-I2of Figure 10.

Figure 13 is a section on theline |3-l3 of Figure 1l.

Figures 14 and l5 are plan and side views of a portion of the apparatusfor drying the sheet material.`

Figures 16 and 17 are sections respectively on the lines Iii-I6 andIl-i'i of Figure 14.

Figures 18 and 19 are plan and side elevations of the intermediateportion of the drying apparatus.

Figures 20 and 21 are sections respectively on the lines 2li-20 and2i-2I of Figure 18.

Figures 22 and 23 are plan and side views respectively of anotherportion of the drying apparatus.

Figure 24 is a section on the line 22-24 of Figure 22.

Figures 25 and 26 correspond respectively to Figures 1 and 4 of thedrawings but show a modified arrangement.

Figures 2'7 and 28 are side and end views, respectively, of a form ofdevice which may be employed if desired for conveyor belt guidingpurposes, and

Figure 29 is an end view of an alternative means for maintaining aconveyor belt in transversely ilat condition.

The improved apparatus herein contemplated embodies a metallic belt 25which may be of brass, stainless steel or other metals provided with asuitably polished or otherwise treated, coated or plated surface. Ifbrass is employed it may be buied to a very high polish and if a steelis employed in the belt a satisfactory surface may be provided byplating the belt with nickel or some other metal which produces asatisfactory, smooth finish. In one embodiment of the apparatus theconveyor 25 is approximately one hundred and sixty feet long. The lmforming solution is delivered to the belt where it passes around a drum25. The solution is spread to form a illm of the desired thickness onthe conveyor belt 25 which carries the film into a drying oven. As shownin Figure 1, the oven is represented in its entirety at 21.

The oven 2l is divided into three sections, each of which is suppliedwith hot air, the arrangement including means whereby the temperature ofthe air supplied to each section may be controlled and adjustedindependently of the other sections.

The conveyor belt 25 is supported at one end by the drum 26 and at itsother end by a drum or roller 28. The film of materialadheres to thebelt to such an extent that the 111m will continue to travel with thebelt on its return reach until the lm is separated from the belt andconducted to winding mechanism indicated at 29.

ported solely by the rolls or drums 2l and 23. The oven 21 is shapedlongitudinally to correspond to the common catenary curve of the belt,thereby avoiding the provision of excess space in the oven which wouldabsorb some of the heat supplied to it and thereby hinder the dryingoperation. 'I'he oven 21 may be made of suitable material, for example,galvanized sheet metal on an angle iron or like frame structure. Theoven may and preferably should be provided with suitable thermalinsulation to assist in maintaining the desired temperatures therein.Such details of the oven construction are not herein illustrated sincethey are not a part of the present invention.

When the protein sheet is to be formed from a base of casein solution,the` casein solution or dispersion has added to it a predeterminedproportion of formaldehyde, or other suitable hardening or settingagent. The solution, or dispersion, begins to set almost as soon asformaldehyde is added to it. It is desirable that the solution bedelivered to the sheet or web forming apparatus before the solution setsto any appreciable extent. Accordingly, the present apparatus providesfor the mixing of the casein solution with the proper amount offormaldehyde at a point immediately preceding the delivery of thesolution to the forming apparatus.

As best shown in Figure 5, the casein solution is conducted to theapparatus b y a pipe line 30 which is connected with any suitable sourceof supply. The pipe line 39 conducts the material to a pump 3i which isactuated by an electric motor 32 to a suitable speed reducing device 33and a variable speed driving device 34. 'I'he pump 3l delivers thecasein solution through a pipe line 35 to a mixing device 35 which isactuated by electric motor 31 or by other suitable means. Theformaldehyde solution is conducted from a suitable source of supply by apipe line 38 to a pump 39 which is actuated by the motor 32 through thespeed reducing and speed controlling units 33 and 34. 'I'he pump 39delivers the formaldehyde through a pipe line 49 into the mixer. Bysuitable valves not herein illustrated, or by proper selection of thecapacities of the pumps 3i and 39, the proportion of the fonnaldehydeand casein solutions may be accurately controlled. Also, the volume ofthese materials delivered to the mixture may be controlled by adiustmentof the speed controlling device 34.

The casein and formaldehyde mixture is delivered by a pipe line 4| fromthe mixer 36 to a header or manifold 42, which is provided with amultiplicity of (in this case 8) discharge outlets which arerespectively connected by exible hoses such as 43 to nozzles or deliverypipes 44.

When synthetic resin and other lm forming solutions are employed, theforegoing described arrangement for injecting the hardening, or anysimilar agent, into the solution immediately before delivery thereof tothe lm forming belt, may not be required. I

The nozzles 44 are mounted so that their relationship to the surface ofthe belt 25 may be adjusted to produce the desired results. As shown inFigures 5 and 8, each of the nozzles is carried by a block 45, each ofwhich is mounted on a rod 46. The blocks 45 may be provided withsetscrews (not shown) for locking the blocks and the nozzles in anydesired position of adjustment relative to the conveyor belt, or ifpreferred, the blocks 45 may be xedly mounted on the said rod '2,340,764As indicated in Figure l, the belt 25 is sup-` 43 and the rod mountedfor rotatable adiustmcnt so that all of the nozzles may besimultaneously adjusted relative to the conveyor belt. It will, ofcourse, be understood that both forms of `adjustment may be provided.

The nozzle supporting rod 43 is carried in this instance by means of apair of hangers 41-41 which are vertically slidably mounted in members43-43. I'he members 43-42 are in turn horizontally slidably mounted in abar 4I. The bar 43 is supported for reciprocation in a directiontransverse to the travel of the conveyor belt 25. For this purpose thebar 49 is supported by bearing members 50 which are carried by a U-shaped frame element Il. The U-shaped member 5| is pivotally mounted atthe free ends of its side legs 52-52 on a rod 53 which is carried bysuitable bracket arms 54-54 which are formed integral with or attachedto conveniently located frame portions of the apparatus.

n To eil'ect reciprocation of the bar 43 and thereby reciprocation ofthe nozzles 44 crosswise of the direction oftravel of the belt 25, thebar is connected by means of a link Il to a crank pin 5t carried by arotatably driven member 51. The latter may be mounted for rotation inany conveniently provided bracket and it may be driven by any suitablearrangement. It will be observed that the revolution of the crank pin 53will be transmitted by the link 55 to the bar 43 which will bereciprocated accordingly.

The U-shaped element 5I is provided with rollers such as 58 which areadapted to engage the marginal portions of the surface of the drum 23beyond the respective edges of the conveyor belt 25. A doctor blade 53is adjustably mounted on a transversely extending supporting member 60.The supporting member 89 is provided with laterally extending arms Gl-GIwhich are pivotally mounted at their free ends on a rod B2 which ismounted at its ends in the side members 52 of the U-shaped member.Provision for adjusting the doctor blade carrying member 6a verticallyrelativev to the conveyor member 25 consists in this instance of screwssuch as 63 which threadedly engage suitably tapped openings in theopposite end portions of the supporting member 60. 'I'he screws 63 maybe turned until their lower ends rest on the U-shaped member 58. It willbe apparent that by adjusting the screws 63, the doctor blade and itssupporting member El) may be adjusted to or from the conveyor member 25.A lock nut or similar device indicated at 64 may be provided on thescrews 63 for locking the latter in the desired adjusted position.

The member 69 is preferably made hollow as indicated in Figure 8 and aheating medium such as hot water may be supplied therethrough by aexible hose connection 65 and drained therefrom 'by a similar connectionindicated at 6B. 'Ihe drum 26 is also preferably hollow and adapted tohave its temperature controlled by supplying to the interior of the drumhot water or the like, the same being supplied through a supply pipe 61and drained therefrom by a pipe t8.

The doctor blade 59 may be secured to the supporting member through theagency of screws such as indicated at 69. Provision for adjusting thedoctor blade relative to the supporting member 60 may include screwssuch as indicated at 10 provided withheaded ends 1i which t into slotsor grooves 12 provided in the doctor blade 59. The screws 19 threadedlyengage a suitably tapped opening in bosses such as indicated at 19 whichmay be carried by the supporting member 80. The upper ends of the screwsare preferably squared or otherwise treated as indicated at 14 tofacilitate turning of the screws. By turning the screws 14 afterloosening the screws 69, the doctor blade 59 may be adjusted. Asindicated in Figure 5. the last de, scribed adjusting means is suppliedat relatively short intervals along the length of the doctor blade sothat accurate localized adjustment of the doctor blade may be made. Bythis means accuracy or uniformity-of the thickness of the fllm ofmaterial permitted to pass under the doctor blade on the conveyor beltmay be accurately controlled.

By mounting the nozzles on a pivotally mounted frame such as the frameit is made very easy to swing the entire delivery mechanism anddoctoring mechanism upwardly away from the conveyor belt to facilitatecleaning or other operations on the belt or drum or adjacent parts ofthe apparatus. Also, by mounting the nozzles M for reciprocationtransversely, the formation of ridges in the casein solution adjacentthe doctor blade is eliminated. It will be understood that in the eventthat the delivery nozzles were to remain stationary, the materialdelivered to the conveyor belt would spread l put approximatelyuniformly on the belt but 'that where adjacent streams of the materialcome together they would tend to pile up to form ridges of material.Formation of such ridges is somewhat objectionable in that it tends tointerfere with uniformity of the Web formed on the apparatus.

As best shown in Figure 5, the drum 26 (and thereby the belt 25) isdriven from a suitable source of power such as an electric motorindicated at 15. The motor 15 is suitably connected to a variable speedcontrolling unit 16 which in turn drives suitably journalled shaft 11.The shaft 11 is equipped with a worm gear 18 which meshes with a wormwheel 19 mounted on the tubular shaft 80 of the drum 26.

The shaft 11 is also connected through the agency of suitable gearconnections enclosed in a housing such as indicated at 8| to a shaft 82.The shaft 82 extends transversely of the machine and is equipped at theopposite side of the apparatus with a pulley or sprocket represented at83 which is connected by a chain or belt designated 84 to means fordriving the rotating member 51.

It will be evident that a supply of casein and formaldehyde solutiondelivered vto the band or belt 25 by the nozzles twill be formed into aweb of uniform thickness on the belt incident to the travel of the beltunder the doctor blade. The web of material on the belt enters the upperv portion of the adjacent end of the drying oven 21 as best shown inFigure l.

It is subjected to heat as soon as it enters the drying oven. Hot air isinitially supplied to the oven adjacent the other or far end thereof,that is adjacent the belt supporting roll or drum 28.

Fior convenience, in reference to the latter end of the apparatus, itwill be identified by the reference numeral 85.

Referring to Figures 22 :to 2.4, inclusive, it will be seen that thereis provided a blower 88 connected by a conduit 81 to branching conduits68, 89 and 90. The conduits 88, ,89 and 90 are respectively connected tothe end portion 85 of the oven near the top, central and bottom portionsthereof as shown. By this arrangement a desirable uniformity of thedistribution of hot air is obtained in the oven. 'I'he blower 86 isconnected to a heating unit 9| which preheats air supplied theretothrough a suitable filtering device indicated at 92. By employing thefiltering device 92, dust and other foreign matter is adequately removedfrom the air which is heated and delivered to the oven so that theprotein sheet formed on the conveyor belt is kept clean and free fromdust and other matter which might impair' its finish. Suitablethermostatic controls (not shown) may be provided for governing thetemperature to which the air is heated by the heating unit 9|.

A similar heating arrangement is provided for supplying hot air to theintermediate portion of the oven. such arrangement being illustrated inFigures 18 to 21, inclusive. By reference to the last mentioned figuresit will be seen that there is provided a blower 98 which is connected bya conduit 94 to conduit branches 95, 96

and 91, which enter the oven 21 by means of delivery nozzles whichdirect the air away from the adjacent exhaust connections as mostclearly shown in Figure 19. Ihe air supplied to the branches 95, 96 and91 is obtained primarily from the adjacent end portion of the furnace towhich hot air is supplied by the blower 86. For this purpose there isprovided a conduit 98 which has vertically spaced exhaust connectionsindicated at 99-99 to the oven immediately preceding the point to whichhot air is delivered thereto by the branches 95, 96 and 91. The conduit98 also has an intermediate connection indicated at |00 which connectswith both the upper and lower sections of the furnace. By reference toFigures 1 to 4, inclusive, it will be observed that the oven is providedinteriorly with hollow sheet metal fillers designated |0|, |02, and |03,respectively, which in effect divide-the furnace into upper and lowerpasses for the upper and lower reaches of the conveyor belt 25. Byproviding the inlet and transverse 'wall in the oven intermediate theadjacent ends of the fillers |0|, |02 and |03. It is likely that some ofthe hot air from one section of the furnace passes directly into theother section but the volume thereof is so small that it has noobjectionable effect on the re-heated air which is supplied throughconduits such as 95, 96 and 91.

A fresh supply of air may also be injected into the furnace by theblower 93, and an intake |04 being suitably connected to the conduit 98for this purpose. The inlet IM is also preferably provided with meansfor filtering the fresh air drawn into the system and a heating unit|05, similar to the heating unit 9|, is provided for heating the airdelivered to it by the conduit 98.

Hot air is supplied to the receiving end portion of the furnace by meansof a'blower |06. The blower |06 receives the hot air from a conduit |01which has exhaust connections I08|08 to the upper and lower passes ofthe intermediate section of the furnace and also an intermediateconnection |09. The hot air drawn from the intermediate furnace sectionis blown by the blower |06 through a delivery conduit IIO to branchconduits |I| and H2, which communicate as best shown in Figures 3. 15and 17 with the upper chamber or pass of the furnace.

To more effectively separate the upper and lower passes of the furnacefrom each other, there is provided a divider H3 as indicated. Forpractical purposes it is neither necessary nor desirable to reheat theair before its delivery to the receiving end portion of the furnacewherefor there is provided `no means for heating the air delivered bythe blower |06; however, it will be understood that if it should bedesired to reheat the air, heating units such as 9| and |05 may beprovided and suitably interposed in the air circuit.

The lower section or pass of the furnace under the receiving end portionof the upper pass is preferably supplied with tempered and hunildied airsupplied thereto by an air conditioning unit II4. The air conditioningunit |I4 may include a suitable blower for impelling the airtherethrough and it is connected by means of a conduit I I to an outletin the delivery end portion of the lower pass of the furnace, asindicated at II6. 'Ihe air exhausted from the delivery end of the lowerpass of the furnace through the conduit I I 6 is returned to the lowerpass of the furnace through a conduit I I1 which has branches IIB andIIS, respectively, connected as indicated at and |2| to the top andbottom of the lower pass of the furnace as best shown in Figures 3, 15and 17. Dampers such as indicated at I22 may be provided in the variousconduits wherever desired for controlling the volume or Velocity of theair drawn from and delivered to the various portions of the furnace.

It has been found that a metal conveyor belt or band such as tends tocurl transversely of its length, i. e. buckle so that on its upper reachit is lower in its middle than at its edges. For the purpose ofcounteracting the tendency of the belt to buckle as explained, there isprovided straightening apparatus shown in Figures 10 to 13, inclusive.Such apparatus is located at a convenient point,'preferably about themiddle of the length oi' the conveyor or at the closest point of thecatenary curve of the belt. The device in its entirety is indicated at|23 in Figure 3 and a similar device for straightening the lower-reachof the belt is indicated at |24.

The device |23 for counteracting the tendency of the upper reach of thebelt to buckle comprises a pair of rolls |25-I25 which are rotatablymounted at their opposite ends in angle iron or other suitable framepieces |26. The frame pieces |28 and the parts carried thereby areprovided with axially vertical bearing elements |21 which slidably fiton vertically extending guide rods |28. The guide rods |28 are supportedby means of suitable brackets as indicated in Figure 10 which are inturn secured to the frame work or sides of the oven. The rolls I25-I25underlie the upper reach of the conveyor band 25 and the latter ismaintained in contact with the rolls |25 across the entire width of theband by means of a series of grooved rollers |29 which are rotatablymounted on the frame members |26. The grooves in the rollers |29 aremade deep enough to receive suiciently wide marginal portions of thebelt to prevent said marginal portions from springing out of thegrooves. Hence the frame members |26 and the parts carried thereby are,in eiect, suspended from the side marginal portions of the conveyorbelt. The weight of the straightening apparatus is such that it isenough to hold the conveyor band to a substantially fiat conditiontransversely of its length and in which condition the band will engagethe entire length of the rolls |25. The weight of the straighteningdevice is not suincient to effect inverted buckling, the latter beingresisted by the support of the rolls |25. It will k` i c be observedthat the straightening apparatus described more or less floats on theguide members I28-|28, the device being supported by the engagement ofthe grooved rollers |29 with the opposite margins of the belt.

The lower or return reach of the belt has the same tendency to bucklebut themarginal portions of the belt in the lower reach tend to assume aposition lower than the central portion of the belt. For the purpose ofresisting such tendency in the lower reach of the belt a floatingstructure substantially like that above described is employed but therolls |25 are replaced by rolls |30 which engage the top surface of thelower 'reach of the belt. The device, is, however, more or lessiioatingly supported by engagement of grooved rollers such as |29 withthe marginal portions of the conveyor belt.

Because of unavoidable inaccuracies in adjustment of the drums or reels26 and 28 relative to each other, or due to other causes, there is atendency for the conveyor belt to shift sidewise; to control andcounteract such tendency there is provided a guiding or steering roll|3I (see Figures 6 and 9) which underlie the lower reach of the belt ata convenient point outside of the drying furnace. 'Ihe roll |3I isjournalled at one end in a suitable bearing |32 and at its other end ina bearing |33 which is mounted for lateral adjustment in a supportingmember |34. The bearing |33, in a neutral position, would be so locatedthat the axis of the steering roll |3I would be exactly perpendicular tothe length of the belt 25. To steer the belt to one side or the otherthe roll I3I is adjusted to an inclined position relative to the lengthof the conveyor belt with the result that it eiects the desired shiftingof the belt.

For effecting shifting of the roll I 3| to inclined position for thepurpose indicated, there is provided a reversible electric motbr |35which is equipped with a worm gear |36 meshing with a worm wheel |31.The worm wheel |31 is secured to one end of a shaft |38 which isjournalled in a suitable portion of the supporting member |34 andprovided with screw threaded engagement with the bearing |33. It will beapparent that when the motor |35 is energized to rotate in eitherdirection, the bearing member |33 will be shifted one way or the otherso as to cause the roll |3I to assume the desired angular position.

The operation of the motor |35 is controlled by a gauging devicecomprising a bell crank |39 which is pivotally mounted intermediate itsends on a suitable post I 40 which is secured to the frame work of theapparatus. The free end of one arm of the bell crank I 39 is equippedwith a roller |4| which is grooved to receive the marginal portion ofthe conveyor belt 25. The free end of the other arm of the bell crank isconnected by a spring |42 to a fixed part of the frame work of theapparatus, such spring tending to rock the bell crank I 39 in the properdirection to maintain the roller |4I in engagement with the edge of theconveyor belt. The free end of said other arm of the bell crank is alsoconnected by means of a Wire or rod |43 to a movable switch arm orcontact member |44 of a two-way switch I 45. A spring |45 connectedbetween said switch arm |44 and a xed point serves to pull the switcharm 44 in a crosswise direction (as diagrammatically represented inFigure 9) to make contact with a contact element |41 of the switch. Suchmovement of the switch arm is, of course, permitted only should be notedthat the travel of the conveyorwhen the bell crank |39 is rocked byoutward movement of the roller |4| resulting from shifting of theconveyor belt in one direction. In the event that the conveyor beltshifts in the other direction and permits the spring |42 to pull the rod|43, the switch arm |44 will be caused to engage the contact element |48of the switch |45.

The two-way switch |45 is connected with suitable relays indicated at|49 and |50 'which respectively control electrical circuits foroperating the motor |35 in opposite directions. It will be seen that byproper adjustment of the twoway switch |45, the extent to which theconveyor belt 25 may shift sidewise may be effectively limited andcontrolled.

The film which is designated is removed from the conveyor belt 25closely adjacent the discharge outlet |52 in the drying furnace. The webor sheet of material |5| is guided around upper and lower rolls |53 asbest shown in Figures 2 and 6 and then downwardly and horizontally undera guide roll |54. From the guide roll |54 .the sheet |5| passes overaguide roll |55 which has associated with it trimming wheels |56|56 fortrinrming the sides of the web so as to provide straight edges and tomake the width ofv the sheet uniform throughout its length. As bestshown in Figure '1, the trimming Wheels |56 are mounted on a shaft |51and they cooperate with the opposite ends of the roll |55 for trimmingthe sheet or web |5| The roll |55 is carried by a shaft |56 which issuitably journalled for rotation and the shaft |51 is also rotatablysupported in suitable bearings provided in frame elements as shown. Thetrimming wheels |58 and the roller |55 are rotated as an incident to thegearing |59 which connects the shafts |51 and |58 and the engagement ofa. pulley |60, c arried by the shaft |51, with a driving belt |6|. Thebelt |6| is driven by a pulley |62 (see Figures 5 and 6) which iscarried by a shaft |63 and which shaft is driven by a belt |64. The belt|64 is driven by engagement with a pulley |65 carried by the drivenshaft 82'.

The material to be Wound or reeled is wound on a suitable core such asindicated at |66 which may be carried by a shaft |61. The shaft |61 isjournalled at one end in a bearing |68 and at its other end is supportedin a. suitable clutch element |69 which is connected with the armatureof a magnetic coupling device indicated in its entirety at |10.

The magnetic coupling device may be in the form of a modified electricmotor to which current may be supplied through an adjustable or variableresistance device |1|. The field portion of the coupling device may bedriven by means of a belt |6| as shown in Figures 6 and '1 and as anincident to the magnetic coupling, the armature portion of the device isalso driven so ,that the clutch element |69 will impart rotation to theshaft |61 and core |66. The magnetic coupling device |10 may be of anyselected form wherefor the details thereof are not herein speciflcallyset forth. By varying the strength of the electric current supplied tothe coupling device, the tension under which the sheet is wound upon thecore may be. varied to suit speciic requirements. If a, strong currentis supplied to the coupling device the sheet will be wound tightly onthe core, but if a weak current is supplied the sheet will be wound lesstightly. It

belt 25 of the machine proceeds at a constant, fixed rate so that byvarying the force which rotates the core |66 the winding tension isaccordingly varied.

In one practical embodiment of the described apparatus, the conveyorbelt 25 is operated at a speed of about fty feet per minute. Transparentcasein sheet material may be eiliciently produced with the apparatus andthe effective control of the drying conditions in the oven of thevariable temperatures in the successive stages of the oven through whichthe belt travels permit the production of unusually clear, transparentmaterial, free from discoloration by scorching or other causes resultingfrom the employment of heat for drying purposes. Also, by permitting agradual increasing of the tem- -perature to which the sheet is subjectedin the drying furnace, thorough drying from the surface of the metallicbelt to the outer or upper surface of the sheet is effected. In otherwords, the formation of a moisture retaining skin on the top surface ofthe sheet as an incident to the immediate application of hightemperature is effectively avoided.

Instead of the above described adjustable roll |3| for guiding the belt25, relatively fixed means may be employed for maintaining the belt inits proper position relative to the receiving end drum 26. Such means isillustrated in Figures 25, 27 and 28.

The relatively fixed guiding means is movable vertically but notsubstantially movable transversely of the conveyor belt 25. As-shownbest in Figures 2'1 and 28, the device comprises a pair of angle ironside members |15, |15, respectively located adjacent the opposite edgesof the lower Areach of the belt 25. Tubular rolls |16 extend between theopposite side members and are suitably rotatably mounted in bearingscarried by the' said side members. For engaging the opposite edges ofthe conveyor belt 25, there is provided a pair of grooved wheels |11,|11, each pair of thev said wheels being located substantially inalignment with the axis of each roller |16. The respective groovedwheels |11 are rotatably supported on the ends of arms |18 and are sospaced from each other that the Width of the conveyor belt] 25 tsbetween them substantially as shown. As best shown in Figure 27, thearms |18 are pivoted at |19 intermediate their ends and grooved wheelssuch as |11 are mounted on each end of each of the arms |18. By mountingthe grooved wheels in the manner explained, self-adjustment of thegrooved wheels |11 relative to the side members |15 is permitted toinsure satisfactory contact between each of the grooved Wheels and theedge of lthe conveyor belt without requiring a burdensome degree ofmanufacturing accuracy.

The guiding unit, comprising the side members |15, |15, and attachedparts, is more or less floatingly supported, so that it may readilyadjust itself to the normal vertical position of the lower reach of theconveyor belt on which it acts. As shown in Figures 25 and 27, thedevice is located within the last stage of the drying oven and it isconnected thereto by means of links such as indicated at |80. The linksare pivoted at one end to the walls or frame of the drying oven and attheir other ends to the side members |15 through the agency of bracketssuch as indicated at |8|. The links |80 permit the guiding device tomove vertically but restrain it from horizontal travel with the conveyorbelt. The weight of the guiding device is suitably counterbalanced sothat itdoes not impose a load on the conveyor belt. One way ofcounter-balancing the guiding device is to provide one or morecounter-balancing weights such as |82 connected by suitable ilexiblemeans |88 extending over pulleys such as 84, and connected to theguiding device.

It has been found that the above described guiding mechanism, whenmounted within the drying oven at about one-third of the length of theconveyor belt from the receiving end thereof, will be automaticallymaintained in proper position relative to the drum 26. The maintenanceof the belt in predetermined position on the drum 26 is considerablymore important than positionl ing of the belt on the drum 28 at theother end of the apparatus.

As an alternative to the means |23 and |24 for maintaining the conveyorbelt flat transversely, there may be provided a series of device such asshown in Figures 25 and 29. Such devices comprise a tubular roll |85rotatably mounted at its ends on brackets such as |86, and groovedwheels |87 receiving the opposite edge portions of the conveyor belt 25and also rotatably mounted on the said brackets ite. As shown in Figure29, the grooved wheels itl are spaced from each otherv so that the widthof the conveyor belt 25 ts between the grooved peripheries of the wheelsso that the top and bottom anges of the wheels engage surface portionsof the belt to prevent its curling and to maintain the belt in flatcondition against the surface of the roll |85. Such devices may besuitably mounted through the agency of brackets |82 on guide rods suchas indicated at |82 which may be mounted in the oven structuresubstantially as above explained for the guide rods H28. However, ifpreferred, the rollers |85 and associated parts may be floatinglysupported by means such as above described for the guiding devicescomprising the rollers |16 and the grooved wheels |11. As shown inFigures 25 and 26, a series oi four of the described devices areprovided at suitably spaced intervals for maintaining the belt at; moreor less may be employed as desired and found advisable.

The described apparatus may be employed as already indicated for theproduction of sheet material of single ply thickness. However, ifdesired, the sheeting may be made multi-ply or laminated by the simpleexpedient of depositing additional coats of the forming liquid onpreceding plies, which in that case are not stripped from the belt untilthe desired number of plies have been formed. Such material, although oflaminated construction, will have the characteristics of a relativelyheavy single-ply sheet since the new plies tend to fuse themselves tothe previously formed plies.

In some cases the rst ply of material may be formed of cellulose acetateor nitrate, or any natural or synthetic resin, or rubber composition toprovide a` backing of water-proof or other selected character.

In some instances, it is desired to apply reading material or the likeon the lsheet material and this may conveniently be done by printing onthe conveyor belt with suitable printing ink 70 or the like which willadhere strongly to the sheet formed on the belt and will be strippedfrom the latter when the sheet is removed from the belt.

Another method of marking the sheet material which may conveniently bepracticed in connection with the formation of the sheeting is to applythe desired reading or display material on the belt with suitablepigmented material such as a paint which is dull or flat, and whichstrongly adheres to the belt. When a sheet is stripped from a beltbearing such indicia, the sheet will disclose the same indicia in theform of frosted or like areas. corresponding to the pigmented areas onthe belt.

It is desirable that means be provided for facilitating the cleaning andpolishing of the conveyor belt 25. Such means may comprise a suitablebufling wheel or drum rotatably supported by frame work |8| and drivenby means such as an electric motor |92. The buillng drum |90 shouldpreferably be mounted so as to be adiustable toward and from theconveyorl belt so as to permit adjustment of the pressure with which thebuillng drum acts on the belt. 'I'he buing device may be operated at anydesired time but it is preferable that it be not operated during theproduction of sheet material .on the belt.

AThe apparatus described may be modified in various ways withoutsacriilcing the advantages set forth in the foregoing description andwithout departing from the spirit of the invention, the scope of whichshould be determined by reference to the following claims, the samebeing construed as broadly as possible consistent with the state of theart. t

I claim: t

1. The method of making sheet material which consists in forming a iilmoi' liquid material on a conveyor belt, propelling the conveyor belt andthe iilm thereon through a multi-stage drying oven, applyingsuccessively increased drying temperatures to the web in a series ofsuccessive stages of the oven, then subjecting the illm to successivelyreduced drying temperatures in successive stages of the oven, andthereafter removing the ilnished web from the conveyor belt.

2. The method of making sheet materia; which consists in forming a iilmof liquid material on a conveyor belt, propelling the conveyor belt andthe mm thereon through a multistage drying oven, applying successivelyincreased drying temperatures to the web in a series of successivestages of the oven, then sub- Jecting the lm to successively reduceddrying temperatures in successive stages of the oven, moistening the airin the last stage of the oven, and thereafter removing the finished webfrom the conveyor belt.

3. In a machine of the character indicated, the combination of a.conveyor belt, means for propelling said conveyor belt, means fordelivering a plurality of streams of predetermined liquid mixture orsolution to said conveyor belt, means located in proximity to saidnozzles for effecting mixture ofgat least two component solutions, andmeans for delivering predetermined proportions of' said componentsolutions to said mixing means.

EDOUARD M. KRATZ.

